Protein fiber and method



United States Patent 2,992,933 PROTEIN FIBER AND METHOD Michael M.Besso, Bethlehem, Pa., Alfred F. Diorio, Washington, D.C., and Walter L.Hochner, Jamaica, N.Y., assignors to National Lead Company, New York,N.Y., a corporation of New "Jersey No Drawing. Original application Mar.25, 1957, Ser. No. 648,002. Divided and this application Mar. 6, 1958,Ser. No. 719,487

3 Claims. (Cl. 106-154) This invention relates to novel protein fibersand to methods for preparing the same. In particular, this inventionrelates to fibers made by solubilization, spinning and coagulation ofnatural proteins such as linseed protein.

Many methods have been proposed for solubilizing and regeneratingnatural proteins, wherein the regeneration is accomplished undercontrolled conditions to convert the protein to a fibrous form similarto natural proteinfibers, e.g. wool. The properties of fibers madeaccording to these processes vary widely, depending partly on thecomposition of the protein itself and partly on the conditions oftreatment, and the manufacture of synthetic protein fibers is still alargely empirical operation.

One method heretofore proposed for the manufacture of protein fibers wasto dissolve the natural protein material in alkali and extrude thealkali solution through spinnerets or the like into an acid bath. Theacid in the spinning bath neutralized the alkali and precipitated theprotein in the filamentary form given it by the spinning operation. Suchfilamentary materials were then washed free of the salt, acid and/ oralkali, stretched to orient the molecules of the fiber, and subjected tovarious treatments such as immersion in formaldehyde solution, etc., inorder to set the fibers in the oriented state, thereby producing astrong, stable protein fiber. Such methods were quite successful in manyrespects, but sufiered from certain disadvantages. Frequently, forexample, the alkali solution was unstable, and could not be stored forany length of time without danger of premature gelation, or degradationof the protein.

Another previously proposed process involves no actual dissolution, butmerely a dispersion of the protein in water, aided by the presence oflarge amounts of wetting agents, for examplaan amount equal to theweight of protein, followed by extrusion of the dispersed protein into asalt bath. The salt bath coagulates the protein in its extrudedfilamentary form, and the resulting fiber is stretch-oriented, washedfree of detergent and set and dried in a manner analogous to thatemployed with protein fibers spun from alkali solutions. This procedure,also, was acceptable in most respects, but also suffered from somedisadvantages, among which may be men tioned the necessity of washingwith acetone or the like to remove the detergent from the spun fiber. Ifthis was not done, the detergent caused the fibers to fuse together intoa form approaching that of a monofilament, thereby losing the desiredproperties.

In addition to the above disadvantages, many of the processes heretoforeproposed suffered from the additional disadvantage that they dependedupon the use, as raw materials, of proteins suitablefor humanconsumption, e.g. casein, egg albumin, peanut protein, etc.

An object of this invention, therefore, is to provide an improvedprotein fiber. Another object is to provide an improved method for thepreparation of such a fiber. Still another object is to provide a methodfor the production of protein fibers which employs a spinning dopecapable of being stored for appreciable lengths of time. A. furtherobject is to provide a method for the preparation of protein fiberswhich does not require removal of detergents from the fiber after thespinning operation. A still 'ice further object is to provide a methodas aforesaid, which does not depend on the use of raw materials suitablefor use as human foodstuffs. Other objects and advantages will becomeapparent from the following more complete description and claims.

Broadly, this invention contemplates a method for the production of afibrous protein material which comprises the steps of forming a mixturecomprising a protein, an organic sulfonate detergent, a strong alkaliand water, said protein being present in amount between 12 and 16% basedon the weight of said mixture, said protein and said detergent beingpresent in relative proportions between 77 parts by weight of protein to23 parts of detergent and 83 parts by weight of protein to 17 parts ofdetergent, and said alkali being present in amount suificient to impartto said mixture a pH between 11.8 and 11.9; passing said mixture througha constricted zone to form a filament thereof; immersing said filamentin an acid-bath to coagulate said protein, thereby converting the sameto a fiber; and stretching, curing, washing, and drying said fiber.

This invention also contemplates a textile fiber consisting essentiallyof a regenerated protein containing, in chemical combination therewith,an organic sulfonate.

Proteins in general may be converted to fibers by the process of thisinvention, provided they are capable of being solubilized by strongalkalis at a pH between 11.8 and 11.9. Among such proteins andproteinaceous materails containing them may be mentioned casein, eggalbumin, blood serum albumin, collagen, gelatin, agar-agar, keratin andkeratinous materials such as wool, animal and human hair, fur, feathers,fish scales and bones, and the like, as well as vegetable proteins suchas soy bean and peanut proteins, castor bean protein, and particularlylinseed protein.

Methods for extracting such proteins from natural proteinaceousmaterials are well known in the art. In the case of linseed and castorbean proteins, a most effective method is the extraction with NaOH or NaS of the meal remaining after the extraction of the linseed or castoroil, and the subsequent reprecipitation of the protein with a suitableagent such as sulfur dioxide.

The organic sulfonate detergent may in general be any of this well-knownclass of detergents, including both alkyl and aryl sulfonates whereinthe alkyl or aryl group, respectively, is sufiiciently large to impart ahydrophobic, organophilic nature to the organic portion of the molecule.Such detergents are discussed, for example, in U.S. Patent No.2,425,550, column 2, line 52 to column 3, line 18. Among the preferreddetergents there mentioned, which are also preferred in the practice ofthe present invention, are commercial sodium alkyl benzene sulfonatewherein the alkyl group contains from 12 to 18 carbon atoms, sodiumdecyl benzene sulfonate, sodium dodecyl. benzene sulfonate, andpolyalkyl monosodium benzene sulfonates where the sum of the carbonatoms in the several alkyl groups is in the neighborhood of 10. Alsosodium isopropyl naphthalene sulfonates, and other organic sulfonatessuch as sulfonated castor oil. These sulfonates will normally beemployed as the sodium organic sulfonates, although the organicsulfonates of other alkali metals or the organic sulfonic acidsthemselves may be employed if desired.

The concentration of protein in the spinning dope (i.e. the mixture ofprotein, detergent, alkali and water) should be not less than about 12nor more than about 16 percent by weight, based on the weight of thedope. If the concentration is too low, i.e., below about 12% by weight,the resulting fiber will lack strength. If the concentration is higherthan about 16%, on the other hand, it. will be difficult or impossibleto put the protein in solution.

The ratio of detergent to protein is critical. If there is less thanabout 17 parts by weight of. detergent for every 83 of protein, it isimpossible to secure satisfactory colloidal dispersion of the protein,and the protein will either gel and be impossible to spin, or at bestwill spin to a non-homogeneous filament lacking sufiicient strength tobe stretch-oriented and incapable of forming a fiber. n the other hand,if the ratio is higher than about 23 parts of detergent to 77 parts ofprotein, it is necessary to remove the detergent by a subsequent acetonewash or equivalent operation, for if such large amounts of detergent areleft in the fiber, the fibers will fuse together during subsequenttreatment.

In the process of this invention, such fusion does not take placebecause of the relatively smaller amount of detergent employed, and itis consequently unnecessary to remove the detergent by a subsequentacetone extraction or equivalent operation. Not only unnecessary, it isundesirable to resort to such an extraction or to remove the detergentin any way, for according to this invention, about two-thirds of thedetergent actually becomes a part of the spun fiber forming thereby aprotein detergent fiber in a ratio between about 85 parts of protein toabout 15 parts of sulfonate and about 89 parts of protein to about 11parts of sulfonate. Somewhat surprisingly, the presence of thedetergent, once it has been incorporated into the molecule, actuallyenhances the water-repellancy of the finished fiber. The reason isbelieved to be that the sul-fonic acid portion of the detergent, whichnormally contributes hydrophilic properties, is blocked by reaction withhydroxymethyl or similar groups in the protein molecule, while thehydrophobic organic portion of the detergent, instead of the originalhydroxymethyl or other hydrophilic group, is presented as the surface ofthe fiber.

The pH of the solution is highly critical. If the pH of the proteinsolution is higher than about 11.9 degradation of the protein willoccur, accompanied by a drop in viscosity, making extrusion impossible.

If, on the other hand, the pH of the protein solution is less than about11.8 the protein-detergent complex will be too thick for extrusion andgelation will occur within a few hours. The pH is controlled by theconcentration of alkali. The exact amount of alkali required toestablish the necessary pI-I condition will vary somewhat depending onthe choice and concentration of the other ingredients of the mixture,and of course upon the particular alkali chosen. In the case of NaOH,amounts between 4% and 6% are generally required to produce the'requiredpH. The amount of alkali should be controlled, however, by directmeasurement of the pH.

As suggested above, any strong alkali may be used in the process of thisinvention. Ordinarily, however, there is no advantage in using any butthe most abundant one, viz. NaOH.

The operation of forming a liquid filament of the protein solution andof coagulating the liquid filament in an acid bath to form a fiber maybest be carried out according to techniques familiar to the art, e.g. byforcing the solution through a submerged spinneret directly into an acidspinning solution. A suitable acid bath for this purpose is dilutesulfuric acid, having a pH of about 1.0. Preferably, the acid solutionis saturated with a salt such as MgSO in order to prevent swelling.

The fiber is then removed from the spinning bath and washed to removeexcess sulfuric acid and salts. At this point, the fiber is ready to bestretch-oriented. It is preferable, although not always necessary, tosubject the fiber before stretching to a pre-cure delay treatment, whichpartially hardens the fiber, and gives it additional strength towithstand breakage during the stretching. A suitable treatment for thispurpose consists of a -minute immersion at 30 C. in a bath containing10% aluminum sulfate, 10% sodium sulfate and 1.5% formaldehyde.

If the pre-cure delay't-reatment is employed, it is followed .by anotherwash and then stretch-oriented. The

stretching is also a technique well known to the art and neednot bedescribed in detail. It has been found satisfactory to employ a 500%stretch. During the stretching, the fiber is preferably sprayed with asalt solution, e.g. 30% Na SO at 70 C., for the purpose of facilitatingthe stretching operation. If the filaments were not kept moist at thisstage, they would not take the necessary amount of stretch. The salt isused to prevent any possible swelling.

After stretching, the fiber is cured on curing reels or the like, underthe slight tension developed in preventing shrinkage of the fiber atthis stage. A five-hour curing period suflices, if carried out at theproper temperatures, as described later.

During curing, the fibers are set in their stretch-orientedconfiguration by treatment with a strong HCl bath, saturated with analkali chloride such as NaCl, and containing a suitable setting agent. Asuitable setting solution consists of 1.5% HCl, 25-30% NaOl and 2%formaldehyde. Preferably, the exact conditions employed for the settingoperation should be determined experimentally for the particular fiberbeing treated. For most of the protein fibers, when using the settingsolution just described, a suitable set can be obtained by a five-hoursetting cycle, in which the temperature is gradually and steadilyincreased from 45 C. at the start to 70 C. at the end. Alternatively, asimilar set can be obtained by treatment for a longer period at lowertemperatures, e.'g. 16 hours at a steady temperature between 45 and 50C. These conditions may be varied somewhat to accommodate thecharacteristics of the particular fiber. Too stringent or too mild acure, however, results in brittle fibers having a harsh hand, poorflex-stability, and a tendency to disintegrate and dust when beingworked. The setting conditions may be made less stringent either bydecreasing the time or the temperature of the cure, or the concentrationof HCl or formaldehyde in the setting solution, as may be mostconvenient, or may be made more stringent by changing any of thesevariables in the opposite direction.

After curing, the fiber is washed and dried, using scouring agents,softeners, etc. as may be desired. If desired, the fiber can be crimpedat this stage to aid in subsequent processing.

In order to more fully illustrate the nature of this invention and themanner of practicing the same, the following examples are presented:

Example 1 A protein-Water slurry was prepared by mixing parts by weightof linseed protein and 715 parts by weight of water. To the resultingslurry were added 33 parts by weight of a commercial mixture of sodiumalkyl benzene sulfonates in which the alkyl groups range from C to C Asmall amount (0.05 part) of a commercial antistatic agent(polyoxyethylene sorbitan monolaurate) was also added to assist insubsequent handling. The resulting slurry was then solubilized by slowaddition, under agitation at room temperature, of 3 N.NaOH. The additionof NaOH was continued .until the pH had reached 11.9. The product was aclear homogeneous spinning dope.

The spinning dope was extruded through a 5000-hole, IOU-micronspinnerette at a rate of 34 feet per minute into an acid-saltcoagulating bath.

The acid-salt coagulating bath consisted of an aqueous solution of 3%sulfuric acid, saturated with magnesium sulfate, and containing 0.1% ofthe same antistatic agent. The pH of the coagulating bath was. 1.0. Thebath was maintained at a temperature of 25 C. and the residence time ofthe extruded filament therein was approximately 2 seconds.

After emerging from the coagulating bath, thefiber was washed by passingit through a water bath and then subiected "to a pre-cure-delaytreatment which consisted of a fiveminute immersion in a bath containingaluminum sulfate, 10% sodium sulfate and 1.5% formaldehyde.

The fiber was again washed and then stretched by passing it over aseries of rolls of increasing diameter, to approximately 500% of itsoriginal length. During the stretching, the fiber was sprayed with a 30%solution of sodium sulfate at 70 C.

The stretched fiber was then cured by winding it on a curing reel andimmersing the reel for five hours in a setting solution consisting of anaqueous solution of 1.5% HCl, 25% NaCl and 2% formaldehyde. During thecuring cycle, the temperature of the solution was gradually raised from45 C. at the start to 75 C. at the end of the cycle. The fiber was thenremoved from the setting bath and washed and dried in conventionalmanner.

The dry fiber was crimped and cut into staple of approximately 1 /2 inchlength, then carded, drawn off as a roving, and twisted into yarn, allin conventional manner. The yarn was dyed in 2% guinea Green BA. Itaccepted the dye readily, giving an attractive, uniform green color. Thedyed yarn was knitted into a sweater which was found to possess anexcellent so-ft cashmerelike hand and good warmth.

The tensile strength of the dry fiber was approximately 19,000 lbs/in.and had an elongation at break of 25%. In the wet condition, the fiberhad a tensile strength of 13,500 lbs/in. and an elongation of about 35to 40%.

Example 2 The procedure of Example 1 was again repeated, except that thecuring step was carried out for a period of 16 hours at 45 C., insteadof 5 hours at a gradually rising temperature. The properties of thefinished product were substantially identical with those described inconnection with Example 11.

Example 4 The procedure of Example 1 was followed, except that insteadof being used immediately, the spinning dope was aged for 2 days at 25C. before being spun. There was a small amount of protein degradationnoticeable in the 6 thinning of the spinning dope and in a slight lossof tensile strength in the finished product. The dope was stillspinnable, however, and the loss of tensile strength was not serious.

Example 5 The procedure of Example 1 was employed, substituting 100parts of castor bean protein for the linseed protein of Example 1. Theproduct was an acceptable textile fiber.

Protein fibers made according to the present invention are made frominexpensive raw materials, and possess properties equivalent, and insome cases superior, to known natural and synthetic textile fibers. Theyhave good tensile strength and elongation, excellent acid and alkaliresistance, pleasant hand, and are readily dyed in conventional dyesystems. Yarns made from the fibers of this invention may be knittedinto soft cashmere-like materials particularly useful in sweaters andthe like, or woven to produce fabrics suitable for sport jackets,scarves, etc. Blended with other fibers such as wool, rayon, etc., theytend to improve the hand of the fabric, and are particularly useful infabrics for slacks, overcoats and the like. The process is simple andinexpensive to operate.

This application is a division of our copending application Serial No.648,002, filed March 25, 1957.

While this invention has been described with reference to particularpreferred embodiments and illustrated by certain examples, these areillustrative only, and the invention is not to be construed as limited,except as set forth in the following claims.

We claim:

1. A textile fiber consisting essentially of a regenerated protein andan alkyl aryl sulfonate detergent, in a ratio between about parts ofprotein to about 15 parts of sulfonate and about 89 parts of protein toabout 11 parts of sulfonate.

2. A fiber, according to claim 1, wherein said regenerated protein is alinseed protein.

3. A fiber, according to claim 1, wherein said alkyl aryl sulfonate is asodium alkyl benzene sulfonate in which the alkyl group contains from 12to 18 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTSLundgren Jan. 18, 1949 Caldwell Jan. 13, 1953 OTHER REFERENCES

1. A TEXTILE FIBER CONSISTING ESSENTIALLY OF A REGENERATED PROTEIN ANDAN ALKYL ARYL SULFONATE DETERGENT, IN A RATIO BETWEEN ABOUT 85 PARTS OFPROTEIN TO ABOUT 15 PARTS OF SULFONATE AND ABOUT 89 PARTS OF PROTEIN TOABOUT 11 PARTS OF SULFONATE.
 2. A FIBER, ACCORDING TO CLAIM 1, WHEREINSAID REGENERATED PROTEIN IS A LINSEED PROTEIN.